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Re: [Phys-l] [PTSOS] anvil and sledgehammer inertia demo

What is wrong with chasing your tail? Since we don't in principle know what a force is, the only way we can say the forces are balanced is to observe the motion.

joe

Joseph J. Bellina, Jr. Ph.D.
Emeritus Professor of Physics
Co-Director
Northern Indiana Science, Mathematics, and Engineering Collaborative
574-276-8294
inquirybellina@comcast.net




On Sep 29, 2010, at 11:12 PM, Derek McKenzie wrote:


To demonstrate equilibrium i.e. balance of forces, put
the puck "here" and "there" and observe that it remains
at rest. Then give it a push and observe uniform motion.

The vertical forces are balanced. The horizontal forces
are nearly zero.


Just out of interest, how do you justify the claim that the forces are balanced, without chasing your tail?